JP2019068037A - Semiconductor sintered body, electric/electronic member, and method for manufacturing semiconductor sintered body - Google Patents

Abstract

To provide a semiconductor sintered body having improved thermoelectric performance by enhancing electrical conductivity while having low thermal conductivity.SOLUTION: The semiconductor sintered body contains a polycrystalline body. The polycrystalline body includes silicon or a silicon alloy. An average grain size of crystal grains constituting the polycrystalline body is 1 μm or less. Electrical conductivity is 10,000S/m or more.SELECTED DRAWING: None

Description

  The present invention relates to a semiconductor sintered body, an electric / electronic member, and a method of manufacturing the semiconductor sintered body.

  A semiconductor is known to be useful as a thermoelectric material for thermoelectric power generation because of a large electromotive force (seebeck coefficient) per temperature difference. Among them, in recent years, silicon materials have attracted attention because of low toxicity, availability at low cost, easy control of electrical characteristics, and the like.

  In order for a thermoelectric material to have high thermoelectric performance, it is required to increase the electrical conductivity of the material and to lower the thermal conductivity. However, due to the high thermal conductivity of silicon, it can not be said that the thermoelectric performance of the silicon-based material is sufficient.

  On the other hand, in recent years, there is known a technique for reducing the thermal conductivity by nano-structuring silicon by sintering nano-sized silicon particles or the like (Patent Document 1, Non-patent Document 1).

US Patent Application Publication No. 2014/0360546

Bux et al, Adv. Funct. Mater., 2009, 19, p. 2445-2452

  The thermal conductivity of the material can be reduced by nanostructuring as described in US Pat. However, since the electrical conductivity is also lowered due to the nanostructuring, the thermoelectric performance of the silicon-based material is not sufficient.

  In view of the above-described points, an aspect of the present invention has an object to provide a semiconductor material having improved thermoelectric performance by enhancing the electrical conductivity while having a low thermal conductivity.

  One embodiment of the present invention is a semiconductor sintered body containing a polycrystalline body, wherein the polycrystalline body contains silicon or a silicon alloy, and the average grain diameter of crystal grains constituting the polycrystalline body is 1 μm or less. It is a semiconductor sintered compact whose electrical conductivity is 10,000 S / m or more.

  According to one aspect of the present invention, it is possible to provide a semiconductor material with improved thermoelectric performance by enhancing the electrical conductivity while having a low thermal conductivity.

  Hereinafter, embodiments according to the present invention will be more specifically described. However, the present invention is not limited to the embodiments described here, and appropriate combinations and improvements can be made without departing from the technical concept of the invention.

(Semiconductor sintered body)
One embodiment of the present invention is a semiconductor sintered body containing a polycrystalline body, wherein the polycrystalline body contains silicon or a silicon alloy, and the average grain diameter of crystal grains constituting the polycrystalline body is 1 μm or less. And a semiconductor sintered body having an electrical conductivity of at least 10,000 S / m. The semiconductor sintered body according to one aspect of the present invention is a polycrystalline body containing silicon or a silicon alloy, and the average grain diameter of crystal grains constituting the polycrystalline body is 1 μm or less, and the electric conductivity is 10, It is more than 000 S / m.

In the case of evaluating the thermoelectric performance (also referred to as thermoelectric conversion performance) of the thermoelectric material, generally, a dimensionless thermoelectric performance index ZT [-] is used. ZT is determined by the following equation.
ZT = α ² σT / κ (1)
In the formula (1), α [V / K] is a Seebeck coefficient, σ [S / m] is an electrical conductivity (in the unit "S / m", "S" is Siemens, "m" is a meter), κ W / (mK)] represents the thermal conductivity, and T represents the absolute temperature [K]. The Seebeck coefficient α indicates the potential difference generated per unit temperature difference. Moreover, the larger the thermoelectric figure of merit ZT, the better the thermoelectric conversion performance. As is clear from the equation (1), in order to improve the thermoelectric conversion performance ZT, it is desirable that the Seebeck coefficient α and the electrical conductivity σ be large and the thermal conductivity 小 さ い be small.

Silicon is known to have a high Seebeck coefficient α, and the above configuration according to this embodiment can provide a semiconductor sintered body having a low thermal conductivity 且 つ and a high electrical conductivity σ. The thermoelectric figure of merit ZT in (1) can be improved. In addition, silicon is less toxic than materials such as Bi ₂ Te ₃ and PbTe, and can be obtained inexpensively. Therefore, by using the semiconductor sintered body according to the present embodiment, it is possible to provide an environment-friendly thermoelectric conversion element (thermoelectric power generation element) and hence a thermoelectric power generation device at low cost.

(Composition of polycrystal)
The semiconductor sintered body according to one aspect of the present invention is a polycrystalline body containing silicon. Specifically, a silicon-based polycrystal or a silicon alloy-based polycrystal, that is, a polycrystal including silicon or a silicon alloy as a main crystal is preferable. The main crystal refers to a crystal having the largest precipitation ratio in an XRD pattern or the like, and preferably refers to a crystal that occupies 55% by mass or more of the entire polycrystal.

  When the semiconductor sintered body is a polycrystalline body containing a silicon alloy, it may be a solid solution of silicon and an element other than silicon, a eutectic, or an intermetallic compound. Elements other than silicon contained in the silicon alloy are not particularly limited as long as they do not impair the effect of the present invention of improving the electrical conductivity while maintaining the low thermal conductivity of the sintered body, and Ge, Fe And Cr, Ta, Nb, Cu, Mn, Mo, W, Ni, Ti, Zr, Hf, Co, Ir, Pt, Ru, Mg, Ba, C, Sn and the like. One or more of these may be contained in the silicon alloy. Moreover, as a silicon alloy, what contains 2 to 20 mass% of elements other than said 1 type or 2 types of above-mentioned silicons is preferable. Moreover, as a silicon alloy, a silicon-germanium alloy, a silicon-tin alloy, and a silicon-lead alloy are preferable. Among them, a silicon-germanium alloy is more preferable from the viewpoint of lowering the thermal conductivity.

  The semiconductor sintered body is a polycrystalline body having a so-called nano structure in which the average grain size of crystal grains constituting the polycrystalline body is 1 μm or less. The average grain size of the crystal grains is preferably less than 1 μm, more preferably 800 nm or less, still more preferably 500 nm or less, still more preferably 300 nm or less, and still more preferably 150 nm or less. By setting the grain size of the crystal grains in the above range, the size of the crystal grains is sufficiently smaller than the mean free path of phonons in a polycrystal, so that the thermal conductivity can be reduced by phonon scattering at the interface. It becomes.

  Further, the lower limit of the average grain size of the crystal grains is not particularly limited, but can be 1 nm or more in view of manufacturing limitations.

  In the present specification, the average grain diameter of crystal grains is measured by direct observation with a microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Refers to the median value of the longest diameter of the individual crystal grains that make up the crystal.

  The electrical conductivity of the semiconductor sintered body is 10,000 S / m or more, preferably 50,000 S / m, preferably 90,000 S / m or more, and 100,000 S / m or more. And more preferably 110,000 S / m or more. The said electrical conductivity can be made into the value in 27 degreeC. Thus, thermoelectric performance can be improved by having the improved electrical conductivity. In addition, the upper limit of the electrical conductivity of the semiconductor sintered body can be 600,000 S / m or less at 27 ° C., and can be 400,000 S / m or less. The thermoelectric performance ZT can be, for example, 0.2 or more at 527 ° C., preferably 0.3 or more, and further preferably 0.4 or more.

  The thermal conductivity of the semiconductor sintered body according to the present embodiment is preferably 25 W / m · K or less, and more preferably 10 W / m · K or less. The said thermal conductivity can be made into the value in 27 degreeC. The absolute value of the Seebeck coefficient of the semiconductor sintered body is preferably 50 to 150 μV / K, and more preferably 80 to 120 μV / K. The above value can be a value at 27 ° C.

(Dopant)
The semiconductor sintered body of the present embodiment can contain an n-type or p-type dopant depending on the application. The dopant is preferably dispersed uniformly throughout the sintered body. As the n-type dopant, it is preferable to contain one of phosphorus, arsenic, antimony and bismuth singly or in combination of two or more. Further, as the p-type dopant, it is preferable to contain one of boron, aluminum, gallium, indium and thallium singly or in combination of two or more. The conductivity type of the above dopant element is an example, and whether the dopant element functions as a dopant of either n-type or p-type depends on the type of the element constituting the mother crystal in the obtained sintered body and the crystal. It depends on the structure etc.

In the case of an n-type dopant, the dopant concentration in the sintered body is preferably 0.1 to 10 and more preferably 0.5 to 5 in a unit of [10 ²⁰ atoms / cm ³ ]. In the case of a p-type dopant, the dopant concentration in the sintered body is preferably 0.1 to 10 and more preferably 0.5 to 5 in a unit of [10 ²⁰ atoms / cm ³ ]. Since the electrical conductivity can be improved by increasing the dopant concentration, the thermoelectric performance ZT improves, but if the dopant concentration becomes excessively large, the Seebeck coefficient decreases and the thermal conductivity increases, so the thermoelectric performance ZT is It will decrease. However, by setting the dopant concentration in the above range, the thermoelectric performance ZT can be improved.

  The n-type dopant is preferably contained at a concentration such that the Seebeck coefficient of the semiconductor sintered body is −185 to −60 μV / K, and the p-type dopant has a Seebeck coefficient of 60 to 185 μV / of the semiconductor sintered body. It is preferable to be contained at a concentration that gives K.

(Electric and electronic components)
As described above, according to the present embodiment, it is possible to obtain a semiconductor sintered body with high electrical conductivity while maintaining low thermal conductivity. Therefore, it can be used as an electric / electronic member, in particular, a thermoelectric element. Among them, power generation devices utilizing exhaust heat, for example, power generation devices mounted on engines and exhaust systems such as automobiles and ships, power generation devices mounted on heat dissipation systems of heating furnaces used industrially, etc. It can be used.

(Method of manufacturing semiconductor sintered body)
In the method for producing a semiconductor sintered body according to the present embodiment, a particle preparing step of preparing particles containing silicon or a silicon alloy and having an average particle diameter of 1 μm or less, and a film of an organic compound containing a dopant element on the surface of the particles. Forming a film, and sintering the particles having the film formed on the surface to obtain a semiconductor sintered body.

  In the particle preparation step of preparing particles containing silicon or silicon alloy and having an average particle diameter of 1 μm or less, for example, a solid obtained by melting and cooling a material of silicon or silicon alloy as a main crystal is known grinding. By pulverizing according to a method, particles (powder) having an average particle diameter of 1 μm or less can be prepared. In addition, particles (powder) can be synthesized from a raw material of silicon or silicon alloy by using a known crystal growth method such as chemical vapor deposition (CVD).

  The average particle diameter of the particles obtained in the particle preparation step is preferably less than 1 μm, more preferably 800 nm, still more preferably 500 nm, and still more preferably 300 nm. In addition, D90 of the particles is preferably 1 μm or less, more preferably 500 nm or less, and still more preferably 200 nm or less. By setting the particle size of the particles before sintering to the above range, it is possible to obtain a sintered body having crystal grains with a particle size of 1 μm or less and appropriately densified. The lower limit of the average particle diameter of the particles prepared in the particle preparation step is not limited, but is preferably 10 nm or more in view of production limitations. In the present specification, the average particle diameter of particles may be a volume-based median diameter measured by a laser diffraction type particle size distribution measuring device.

  Subsequently, a film forming step of forming a film of an organic compound containing a dopant element on the surface of the particles obtained in the above particle preparation step is performed. This film formation step can be carried out by dispersing the particles obtained in the particle preparation step in a solvent, mixing the organic compounds containing the above-mentioned dopant element, and mixing treatment in a bead mill or the like. The organic compound containing the dopant element may be added to the particle dispersion in the form of a mixture. Thereafter, the solvent is removed by reduced pressure or the like, and the particles are dried to obtain particles in which a film of an organic compound containing a dopant element is formed on the surface. In this case, the thickness of the film may be 0.5 to 5 nm, and is preferably a monomolecular film of an organic compound.

  As the dopant element contained in the organic compound, the above-described dopant element of n-type or p-type can be used depending on the application. The n-type dopant element may be one or more of phosphorus, arsenic, antimony and bismuth. The p-type dopant element can be one or more of boron, aluminum, gallium, indium and thallium.

  The organic compound containing the dopant element may be a polymer or a low molecule. The organic compound may be a hydride containing a dopant element, an oxide, an oxo acid or the like.

  When phosphorus is used as the n-type dopant element, as the organic compound, phosphoric acid, alkyl phosphonic acid, alkyl phosphinic acid and esters thereof, polyvinyl phosphonic acid, trialkyl phosphine such as phosphine, triethyl phosphine, tributyl phosphine, etc. may be used. it can. Alternatively, a polymer containing phosphonic acid (phosphonic acid polymer) may be used. When arsenic is used as the dopant element, arsine or the like can be used, antimony trioxide can be used when antimony is used, and bismuth acid can be used when bismuth is used.

  When boron is used as the p-type dopant element, borane clusters such as decaborane and ortho decaborane, boron trifluoride and the like can be used as the organic compound. When aluminum is used as the dopant element, aluminum trichloride, trimethylaluminum or the like can be used. When gallium is used, gallium trichloride, trimethylgallium or the like can be used. When indium is used. Indium trichloride or the like can be used, and when thallium is used, thallium chloride or the like can be used. The above organic compounds can be used alone or in combination of two or more.

  In the film forming step, the organic compound containing the dopant element is preferably added in an amount of 3 to 60 parts by mass, preferably 10 to 30 parts by mass, with respect to 100 parts by mass of the particles prepared in the particle preparation step. Is more preferred.

  The sintering step is not particularly limited as long as it is a method capable of sintering the above-mentioned raw material particles (powder), but a spark plasma sintering method (Spark Plasma Sintering (SPS)), a pressureless sintering method (Two) Step Sintering, Hot Pressing, Hot Isostatic Pressing (HIP), Microwave Sintering, etc. may be mentioned. Among these, it is preferable to use a discharge plasma sintering method capable of obtaining smaller crystal grains.

  The sintering temperature in the sintering step can be selected according to the composition of the main crystal that is silicon or silicon alloy, but is preferably 900 ° C. or more, and more preferably 1000 ° C. or more. The sintering temperature is preferably 1400 ° C. or less, more preferably 1300 ° C. or less. By setting it as the said range, densification of a sintered compact can be accelerated | stimulated and the average particle diameter of the crystal grain of a polycrystal can be maintained at 1 micrometer or less.

  Moreover, the temperature rising rate in the sintering step is preferably 10 to 100 ° C./min, and more preferably 20 to 60 ° C./min. By setting the temperature rising rate to the above range, uniform sintering can be promoted, and excessively rapid grain growth can be suppressed to maintain the average grain size of the polycrystalline grains at 1 μm or less.

  In the sintering step, pressure is preferably applied. In that case, the applied pressure is preferably 10 to 120 MPa, and more preferably 30 to 100 MPa.

  In addition, in this embodiment, particles containing silicon or silicon alloy and having an average particle diameter of 1 μm or less are prepared, a film of an organic compound containing a dopant element is formed on the surface of the particles, and particles are formed on the surface And sintered to obtain a semiconductor sintered body. Such a semiconductor sintered body has high electrical conductivity while maintaining low thermal conductivity. Thus, a semiconductor sintered body having high thermoelectric performance ZT can be provided.

  As described above, when the particles in which the film containing the dopant element is formed on the surface are sintered, the doping element is thermally diffused from the interface of the particles to the inside of the particles during sintering. Such doping by thermal diffusion from the particle interface can improve the electrical conductivity of the resulting sintered body. In addition, the semiconductor sintered body obtained by the method according to the present embodiment has a comparable dopant concentration, but it is better compared to a sintered body that is doped without using thermal diffusion from the particle interface. It can exhibit high electrical conductivity.

  As described above, in the method according to the present embodiment, doping is performed by causing the film to contain the dopant element in the film forming step, and thermally diffusing from the particle interface in the sintering step. However, it is possible to carry out the above-mentioned film formation step after the dopant is previously contained in the particles at the stage of the particle preparation step. For example, at the stage of melting the material of silicon or silicon alloy as the main crystal, the dopant element alone or its compound is mixed, and the resulting melt is cooled and crushed to prepare particles (powder) containing the dopant. can do. Moreover, when preparing particles using chemical vapor deposition (CVD) or the like, the raw material of silicon or silicon alloy and the simple substance or compound of the dopant element are mixed in the vapor state and condensed to obtain the dopant. The particles can be prepared.

  Thus, doping can be made higher by incorporating the dopant at the stage of the particle preparation step and further thermally diffusing the dopant from the particle surface into the particle by the film forming step and the baking step.

[N-type semiconductor sintered body]
Example 1
(Preparation of silicon particles)
28 g of elemental silicon (purity 99.99% or more) and 1.0 g of elemental phosphorus (purity 99.9%) were melted by an arc melting apparatus under an argon atmosphere, and then cooled. The mass obtained by cooling was rolled again to melt and cool. The melting and cooling were repeated a total of four cycles to obtain a dopant-containing silicon material as a base material. This silicon material was roughly crushed to 45 μm or less using a hammer crusher and a planetary ball mill. Furthermore, it grind | pulverized until D90 becomes about 150 nm using the bead mill. At this time, isopropyl alcohol was used as a medium, and zirconia beads of 0.05 mm in diameter were used as beads. From the resulting slurry, isopropyl alcohol was removed under reduced pressure and further dried to obtain silicon particles.

(Coating of particles)
The obtained silicon particles were dispersed in heptane, and a mixture prepared by adding 1.0 g of polyvinylphosphonic acid (manufactured by Sigma-Aldrich Co.) to 5.0 g of silicon particles was charged into the above-described bead mill, and the mixing treatment was performed for 300 minutes. . Thereafter, heptane was removed under reduced pressure and further dried to obtain monomolecular film-coated silicon particles.

(Sintering)
The silicon particles coated with the monomolecular film were loaded into a die / punch jig made of graphite, and heated to 1200 ° C. using a discharge plasma sintering apparatus to obtain a sintered body. At this time, the pressurizing pressure was 80 MPa, and the temperature rising rate was 50 ° C./min. The outer surface of the obtained sintered body was roughly polished to remove an impurity layer derived from graphite or the like. Furthermore, it cut | disconnected using the dicing saw and obtained the cube-shaped chip | tip.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.1 × 10 ⁵ S / m, and the thermal conductivity was 10.5 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (-89.2 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.30.

Example 2
(Preparation of silicon particles)
As in Example 1, silicon particles were prepared.

(Coating of particles)
A monomolecular film-coated silicon particle was obtained in the same manner as in Example 1 except that a mixture in which 1.6 g of tributylphosphine was added instead of 1.0 g of polyvinylphosphonic acid was used.

(Sintering)
In the same manner as in Example 1, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and furthermore, a rectangular chip was obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. In addition, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon particles having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.0 × 10 ⁵ S / m, and the thermal conductivity was 10.0 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (−94.9 μV / K) of the sintered body, and was 2.1 based on [10 ²⁰ atoms / cm ³ ]. Also, the thermoelectric figure of merit ZT at 527 ° C. was 0.29

Example 3
(Preparation of silicon particles)
Silicon particles were prepared as in Example 1.

(Coating of particles)
A monomolecular film-coated silicon particle was obtained in the same manner as in Example 1 except that a mixture in which 1.0 g of methylphosphonic acid was added instead of 1.0 g of polyvinylphosphonic acid was used.

(Sintering)
In the same manner as in Example 1, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and furthermore, a rectangular chip was obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.1 × 10 ⁵ S / m, and the thermal conductivity was 10.5 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (-91.0 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.30.

Example 3A
(Preparation of silicon particles)
Silicon particles were prepared as in Example 1.

(Coating of particles)
The same as Example 1 except that a mixture obtained by adding 1.1 g of a phosphonic acid polymer mixture (phosphorus content 22 wt%, Nitto Denko Corp. developed product, No. DB 81) in place of 1.0 g of polyvinyl phosphonic acid was used. Thus, silicon particles coated with a monomolecular film were obtained.

(Sintering)
In the same manner as in Example 1, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and furthermore, a rectangular chip was obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.2 × 10 ⁵ S / m, and the thermal conductivity was 10.0 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (−90.1 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.31.

Example 4
(Preparation of silicon particles)
Example except that 0.5 g of single phosphorus (purity 99.9%) and 3.5 g of single bismuth (purity 99.99% or higher) were used instead of 1.0 g of single phosphorus (purity 99.9%) Silicon particles were obtained in the same manner as in 1.

(Coating of particles)
In the same manner as in Example 1, silicon particles coated with a monomolecular film were obtained.

(Sintering)
In the same manner as in Example 1, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and furthermore, a rectangular chip was obtained.
(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electrical conductivity at 27 ° C. of the sintered body was 1.2 × 10 ⁵ S / m, and the thermal conductivity was 9.0 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (−93.5 μV / K) of the sintered body, and was 2.1 based on [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.40.

Example 5
(Preparation of silicon particles)
Using 100 molar equivalents of monosilane (SiH ₄ , purity 99.9%) and 3 molar equivalents of phosphine (PH ₃ , purity 99.9%) as raw materials, reaction is performed by a microwave plasma reactor through an argon / hydrogen mixture. The particles were synthesized and collected by an in-line filter. Silicon nanoparticles were obtained as an aggregate having an average particle diameter of about 150 nm, and the average diameter of the crystallites was 10 nm.

(Coating of particles)
The same treatment as in Example 1 was carried out to obtain monomolecular film-coated silicon particles.

(Sintering)
In the same manner as in Example 1, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and furthermore, a rectangular chip was obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 0.9 × 10 ⁵ S / m, and the thermal conductivity was 8.4 W / m · K. When the dopant concentration was calculated based on the Seebeck coefficient (-95.0 μV / K) of the sintered body, it was 2.0 in units of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.50.

Example 6
(Preparation of silicon alloy particles)
28 g of single silicon (purity 99.99% or higher), 28 g of single silicon (purity 99.99% or higher) and 3.0 g of single germanium (purity 99.99% or higher), single phosphorus (purity 99.9) The particles were prepared in the same manner as in Example 1 except that the amount of%) was changed to 0.5 g, to obtain silicon alloy particles.

(Coating of particles)
The surface of the silicon alloy particles was coated in the same manner as in Example 1 to obtain silicon alloy particles coated with a monomolecular film.

(Sintering)
In the same manner as in Example 1, the silicon alloy particles coated with the monomolecular film were sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of that of the silicon alloy before grinding. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.2 × 10 ⁵ S / m, and the thermal conductivity was 4.2 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (-82.3 μV / K) of the sintered body, and was 3.1 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.54.

[P-type semiconductor sintered body]
Example 7
(Preparation of silicon particles)
28 g of elemental silicon (purity 99.99% or more) and 0.5 g of elemental boron (purity 99.9%) were melted in an argon atmosphere using an arc melting apparatus, and then cooled. The mass obtained by cooling was rolled again to melt and cool. The melting and cooling were repeated a total of four cycles to obtain a dopant-containing silicon material as a base material. This silicon material was roughly crushed to 45 μm or less using a hammer crusher and a planetary ball mill. Furthermore, it grind | pulverized until D90 becomes about 150 nm using the bead mill. At this time, isopropyl alcohol was used as a medium, and zirconia beads of 0.05 mm in diameter were used as beads. From the resulting slurry, isopropyl alcohol was removed under reduced pressure and further dried to obtain silicon particles.

(Coating of particles)
The obtained silicon particles were dispersed in heptane, and a mixture prepared by adding 0.5 g of decaborane to 5.0 g of silicon particles was charged into the above-described bead mill, and the mixing process was performed for 300 minutes. Thereafter, heptane was removed under reduced pressure and further dried to obtain monomolecular film-coated silicon particles.

(Sintering)
The silicon powder coated with the monomolecular film was loaded into a die / punch jig made of graphite and heated to 1200 ° C. using a discharge plasma sintering apparatus to obtain a sintered solid. At this time, the pressurizing pressure was 80 MPa, and the temperature rising rate was 50 ° C./min. The outer surface of the obtained sintered body was roughly polished to remove an impurity layer derived from graphite or the like. Furthermore, it cut | disconnected using the dicing saw and obtained the cube-shaped chip | tip.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. In addition, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon particles having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.1 × 10 ⁵ S / m, and the thermal conductivity was 12.0 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (89.4 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.30.

Example 8
(Preparation of silicon particles)
Silicon particles were prepared in the same manner as Example 7.

(Coating of particles)
A monomolecular film-coated silicon particle was obtained in the same manner as in Example 6 except that a mixture of 1.6 g of tributylborane instead of 0.5 g of decaborane was used.

(Sintering)
In the same manner as in Example 7, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. In addition, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon particles having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.0 × 10 ⁵ S / m, and the thermal conductivity was 11.5 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (93.9 μV / K) of the sintered body, and was 2.1 based on [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.31.

Example 9
(Preparation of silicon particles)
Silicon particles were prepared in the same manner as Example 7.

(Coating of particles)
A monomolecular film-coated silicon particle was obtained in the same manner as in Example 7 except that a mixture in which 1.0 g of triethyl borate was added instead of 0.5 g of decaborane was used.

(Sintering)
In the same manner as in Example 7, the silicon particles coated with the monomolecular film were sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon particles of an average of 100 nm were densely bonded was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.1 × 10 ⁵ S / m, and the thermal conductivity was 12.5 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (89.2 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.30.

Example 10
(Preparation of silicon particles)
Example except that 0.5 g of single boron (purity 99.9%) and 3.5 g of single gallium (purity 99.99% or higher) were used instead of 0.5 g of single boron (purity 99.9%) Silicon particles were prepared in the same manner as 7).

(Coating of particles)
In the same manner as in Example 7, silicon particles coated with a monomolecular film were obtained.

(Sintering)
In the same manner as in Example 7, the silicon powder coated with the monomolecular film was sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

  The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electrical conductivity at 27 ° C. of the sintered body was 1.2 × 10 ⁵ S / m, and the thermal conductivity was 9.0 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (86.6 μV / K) of the sintered body, and was 2.5 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.31.

Example 11
(Preparation of silicon particles)
Using 100 molar equivalents of monosilane (SiH ₄ , purity 99.9%) and 3 molar equivalents of diborane (B ₂ H ₄ , purity 99.9%) as raw materials, they are reacted in a microwave plasma reactor through an argon / hydrogen mixture The nanoparticles were synthesized and collected by an in-line filter. Silicon nanoparticles were obtained as an aggregate having an average particle diameter of about 150 nm, and the average diameter of the crystallites was 10 nm.

(Coating of particles)
The same treatment as in Example 7 was carried out to obtain monomolecular film-coated silicon particles.

(Sintering)
In the same manner as in Example 7, the silicon powder coated with the monomolecular film was sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of pure silicon. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon crystal grains having an average particle diameter of 100 nm were closely joined was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.0 × 10 ⁵ S / m, and the thermal conductivity was 8.8 W / m · K. The dopant concentration was calculated based on the Seebeck coefficient (89.0 μV / K) of the sintered body, and was 2.3 as a unit of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.30.

Example 12
(Preparation of silicon alloy particles)
Example 7 and Example 7 except that 28 g of single silicon (purity 99.99% or higher) and 3.0 g of single germanium (purity 99.99% or higher) were used instead of 28 g of single silicon (purity 99.99% or higher) Particles were similarly prepared to obtain silicon alloy particles.

(Coating of particles)
In the same manner as in Example 7, monomolecular film-coated silicon alloy particles were obtained.

(Sintering)
In the same manner as in Example 7, the silicon powder coated with the monomolecular film was sintered to obtain a sintered body, and a rectangular parallelepiped chip was further obtained.

(Structure and characteristics)
The density of the sintered body measured by the Archimedes method was 98.5% of that of the silicon alloy before grinding. Further, when a cross section of the sintered body was observed by a transmission electron microscope (TEM), a structure in which silicon alloy crystal grains having an average particle diameter of 100 nm were densely bonded was observed.

The electric conductivity at 27 ° C. of the sintered body was 1.0 × 10 ⁵ S / m, and the thermal conductivity was 4.5 W / m · K. When the dopant concentration was calculated based on the Seebeck coefficient (81.2 μV / K) of the sintered body, it was 3.3 in units of [10 ²⁰ atoms / cm ³ ]. The thermoelectric figure of merit ZT at 527 ° C. was 0.41.

Claims (10)

A semiconductor sintered body containing a polycrystalline body,
The polycrystalline body includes silicon or a silicon alloy,
The average grain size of crystal grains constituting the polycrystal is 1 μm or less,
The semiconductor sintered compact whose electrical conductivity is 10,000 S / m or more.   The semiconductor sintered body according to claim 1, containing one or more dopants selected from phosphorus, arsenic, antimony and bismuth.   The semiconductor sintered body according to claim 1, containing one or more dopants selected from boron, aluminum, gallium, indium and thallium.   The semiconductor sintered body according to any one of claims 1 to 3, which has a Seebeck coefficient of -150 to 50 μV / K.   An electric / electronic member comprising the semiconductor sintered body according to any one of claims 1 to 4. Preparing a particle comprising silicon or a silicon alloy and having an average particle size of 1 μm or less;
Forming a film of an organic compound containing a dopant element on the surface of the particle;
And sintering the particles having the film formed on the surface to obtain a semiconductor sintered body.   The method for producing a semiconductor sintered body according to claim 6, wherein the dopant element contains one or more selected from phosphorus, arsenic, antimony and bismuth.   The manufacturing method of the semiconductor sintered compact according to claim 6 in which said dopant element contains one or more chosen from boron, aluminum, gallium, indium, and thallium.   The manufacturing method of the semiconductor sintered compact as described in any one of Claim 6 to 8 which performs the said sintering step at the temperature of 900 degreeC or more.   The method for producing a semiconductor sintered body according to any one of claims 6 to 9, wherein the sintering step includes performing discharge plasma sintering.